The utilization of activated oxygen, or ozone, to clean, disinfect and deodorize is well known. Ozone is created when oxygen comes in contact with either ultraviolet light or electricity. The ultraviolet light or electricity breaks apart some of the oxygen molecules, each of which consists of a pair of oxygen atoms held together by covalent bonds, into a number of singular oxygen atoms. A portion of the number of singular oxygen atoms thereafter reassemble to form ozone (O.sub.3) molecules. The ozone molecules have very high oxidation capabilities, and thus, readily react with metals to form oxides, such as FeO.sub.2 and CrO.sub.2.
For many years, water treatment plants have positioned ozone generators in the wastewater, or effluent, stream to introduce ozone into the effluent. The ozone kills bacteria and inactivates many viruses, fungi and other pathogens present in the effluent. More recently, producers of bottled water have incorporated ozone in the purification process to kill germs and bacteria that might be present in the water. It is also well known to treat laundry with ozone. U.S. Pat. No. 5,097,556 issued Mar. 24, 1992, U.S. Pat. No. 5,181,399 issued Jan. 26, 1993 and U.S. Pat. No. 5,241,720 issued Sep. 7, 1993, all to Engle et al.; and U.S. Pat. No. 5,493,743 issued Feb. 27, 1996 to Schneider et al., each disclose methods and apparatus for utilizing ozone in the laundry wash process to treat laundry wastewater.
The use of ozone in the laundry wash process produces a number of significant environmental benefits and cost savings. For example, when ozone is generated and introduced into the wash liquor during the wash cycle, the activated oxygen attacks the larger soil molecules and fragments them into smaller soil molecules that are more easily acted on by the components of the wash chemistry (e.g., detergents, bleaches, additives and surfactants). Thus, the wash chemistry is more effective in removing the soil from the laundry items. As a result, a greater percentage of the soil embedded in the laundry items dissolves into the wash liquor and is extracted with the laundry wastewater. In addition, the strong oxidizing capabilities of ozone act as a powerful disinfecting and cleansing additive for inactivating contaminants, such as viruses and other pathogens.
Because of the increased effectiveness of the wash chemistry and the oxidizing capabilities of the ozone, the concentration of the wash chemistry in the wash liquor can be substantially reduced. In some applications, the wash chemistry can even be eliminated entirely. Accordingly, fewer chemicals that are harmful to the environment are required to be used and subsequently discharged into the ground or municipal sewer system. The increased effectiveness of the wash chemistry shortens the wash cycle time of the laundry, thereby reducing the amount of energy used by the laundry. The number of rinse cycles and the average rinse cycle time can also be reduced because fewer chemicals must be rinsed and extracted from the laundry items. As a result, the total amount of water needed to extract the soil and wash chemistry from the laundry is reduced. An added benefit of the reduced concentration of wash chemistry, wash and rinse cycle times and number of rinse cycles is that the useful life of the laundry items washed in an ozonated laundry system is increased.
With fewer chemicals present in the wash liquor, the wastewater from the laundry process is less harmful to the environment, and is easier and less costly to treat. Sewage costs have risen dramatically in recent years in response to ever increasing water purification standards. The stricter municipal water purification standards require wastewater, especially from commercial and industrial sources, to be thoroughly treated before the water is returned to the municipal water supply. In some instances, ozone can be utilized in a closed loop laundry machine to treat the laundry wastewater after filtration. The filtered and ozone treated water is then recycled back to the wash liquor for further use by the laundry machine. Accordingly, additional cost savings and environmental benefits are obtained.
For example, ozone has been applied to closed-loop laundry systems (FIG. 1a) which have the capability to recycle the water after each cycle of the wash process. A storage tank 10 is filled with water supplied from a municipal water source in a conventional manner and is re-filled when the water level in the storage tank 10 is low. Ozone generated by an ozone generator 12 is introduced into the water, for example, by pumps or injectors located in the storage tank 10. The laundry machine 14 is then filled with ozonated water at the start of the wash process. During a drain cycle of the wash process, the wash liquor is drained from the laundry machine 14 through filter 16 to collect particulate waste. One or more filters or filter screens can be used to progressively eliminate smaller particles without impeding the flow of the wash liquor. The filtered wash liquor is then diverted to the sewer 18 for further wastewater treatment, for example after a wash cycle, or returned to the storage tank 10 to be re-used, for example after a rinse cycle, thereby creating a closed-loop laundry system. After the wash process has completed a final drain cycle, the filtered wastewater can be diverted to the sewer 18 or returned to the storage tank 10 for re-use.
Ozone has also been applied to open-loop laundry systems (FIG. 1b) which drain and divert the laundry wastewater to the sewer 18 after each wash cycle and after each rinse cycle of the wash process. A storage tank 10 is filled with water supplied from a municipal water source in a conventional manner and is re-filled after each cycle of the wash process. Ozone generated by an ozone generator 12 is introduced into the water, for example, by pumps or injectors located in the storage tank 10. The laundry machine 14 is then filled with ozonated water at the start of the wash process. During a drain cycle of the wash process, the wash liquor is drained from the laundry machine 14 through filter 16 to collect particulate waste. At the end of each cycle of the wash process, the wash liquor is drained, filtered and diverted to the sewer 18 for further wastewater treatment before rejoining the municipal water supply, thereby creating an open-loop laundry system.
Unfortunately, utilization of ozone in laundry systems typically produces off-gases because the concentration of ozone introduced into the laundry wash liquor is maintained at a constant level regardless of the size or content of the particular wash load. In commercial and institutional laundry facilities, various sizes of wash loads and various laundry items are washed. However, as previously mentioned, the concentration of ozone introduced into each wash process is maintained at a constant level. Once the ozonated water is introduced into the laundry machine, agitation of the wash liquor causes the excess ozone to off-gas. Because the size and content of wash loads vary widely in commercial applications, off-gassing occurs whenever a constant level of ozone is introduced into the wash liquor during the wash process. The size and content of the wash load determines the amount of water and wash chemistry needed to clean the laundry, and as a result, the concentration of the wash chemistry in the wash liquor. The constant level of ozone produced by the prior art ozonated laundry systems does not take into account the size and content of the wash load, and thus, the concentration of the wash chemistry in the wash liquor. As a result, off-gassing is certain to occur.
It is also unfortunate that ozone molecules have a tendency to degenerate over time and revert to oxygen molecules and singular oxygen atoms. Accordingly, whenever possible it is preferable to introduce ozone directly into the wash liquor in the laundry machine during the wash process to maximize the benefit provided by the ozone. A number of difficulties, however, are typically encountered when ozone is introduced directly into the wash liquor in the laundry machine. In particular, a secure, fluid-tight connection must be maintained between the injector utilized to introduce the ozone into the wash liquor and the laundry machine to prevent leakage of the untreated wash liquor into the environment outside the laundry machine. However, at the same time it is desirable that the injector be accessible and easily removed for cleaning, repair or replacement. Ozone injectors, and in particular elongate ozone diffuser stones or sparging rods, have previously been inserted through and welded to a wall adjacent the drain of the laundry machine. Oftentimes, however, access to the laundry machine with cumbersome welding equipment is limited. Further, once welded the ozone injector is permanently fixed to the wall of the laundry machine and cannot be readily removed for cleaning, repair or replacement. Still further, welding often causes the metal in the area of the wall of the drain of the laundry machine to weaken, thus increasing the risk that the laundry machine will leak or rupture under the hydrostatic and hydrodynamic forces generated by the laundry machine during the wash process.
As previously discussed, the concentration of the wash chemistry in the wash liquor can be reduced by the addition of ozone. However, current open-loop laundry systems that utilize ozone do not adequately address the opportunity for further reduction of the wash chemistry, energy and water in response to wash loads that vary in size and content. Despite the benefits of using ozone in the laundry wash process, more efficient use of the wash chemistry and further reduction in energy and water consumption are possible. The additional benefits of using less wash chemistry and consuming less energy and water for washing and rinsing laundry are substantial, especially in existing commercial and institutional laundry facilities that wash large quantities of laundry. The open-loop, ozonated laundry systems utilized in existing commercial and institutional laundry facilities, however, are not readily converted to closed-loop, ozonated laundry systems. Such facilities typically utilize a common collection pit, or sump, for collecting and temporarily storing the wastewater drained from one or more laundry machines during a drain cycle as it is filtered and diverted to the sewer. As previously mentioned, closed-loop, ozonated laundry systems divert the wastewater leaving the laundry machine through a particulate filter directly into a storage tank. Heretofore, none of the prior art closed-loop, ozonated laundry systems have been designed to collect the wastewater from one or more laundry machines in a conventional sump, filter and return the wastewater directly to the laundry machines for re-use.
It is therefore apparent that a system and method for treating laundry with ozone is needed that varies the concentration of the ozone in the wash liquor in response to the wash load. Further needed is a system and method for treating laundry with ozone that varies the concentration of the ozone in the wash liquor in response to the size and content of the wash load. Further needed is a system and method for treating laundry with ozone that determines the minimum amount of wash chemistry required and the optimum amount of ozone to be introduced into the wash liquor for various wash loads, thereby reducing ozone off-gassing and further reducing the amount of energy and water consumed to wash and rinse the laundry items. Further needed is a system and method for treating laundry with ozone that includes an adapter for removably securing an ozone injector adjacent the drain of the laundry machine. Still further needed is an ozonated laundry system having the capability to re-use at least a portion of the water from the municipal water supply utilized by the laundry machine during the wash process.